package 第8周_二分搜索树.集合与映射.Map;

public class LinkedListMap<K, V> implements Map<K, V> {

   private class Node{
       public K key;
       public V value;
       public Node next;

       public Node(K key, V value, Node next){
            this.key = key;
            this.value = value;
            this.next = next;
       }

       public Node(K key){
           this(key, null, null);
       }

       public Node(){
           this(null, null, null);
       }
   }

   private Node dummyHead;
   private int size;

   public LinkedListMap(){
       dummyHead = new Node();
       size = 0;
   }

    @Override
    public void add(K key, V value) {
        Node node = getNode(key);
        if (node == null){
            dummyHead.next = new Node(key, value, dummyHead.next);
            size++;
        }
        else {
            node.value = value;
        }
    }

    @Override
    public V remove(K key) {

       Node prev = dummyHead;
       while (prev.next != null){
           if (prev.next.key.equals(key)){
               break;
           }
           prev = prev.next;
       }

       if (prev.next != null){
           Node delNode = prev.next;
           prev.next = delNode.next;
           delNode.next = null;
           size--;
           return delNode.value;
       }
        return null;
    }

    @Override
    public boolean contains(K key) {
        return getNode(key) != null;
    }

    /**
     * 传入一个键， 返回这个键所在的节点的引用
     * @param key
     * @return
     */
    private Node getNode(K key){
        Node cur = dummyHead.next;
        //如果链表不为空
        while (cur != null){
            if (cur.key.equals(key)){
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(key);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K key, V value) {
        //先判断是否有这个键所在的节点
        Node node = getNode(key);
        if (node == null){
            throw new IllegalArgumentException("传入的键不存在");
        }
        node.value = value;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }
}
